Lyme disease (LD) is a recently recognized arthropod-borne human disease caused by the spirochete, Borrelia burgdorferi. The occurrence and distribution of this agent in ticks and vertebrates in Indiana has not been established. However, four unpublished reports of clinical cases of erythema chronicum migrans (an early symptom of LD) in Indiana, and similar reports of cases in neighboring states indicate the likelihood of its presence. Although Ixodes dammini, the primary vector of LD in the Midwest and the Northeast, has not been recorded in Indiana, two other species of ticks, from which B. burgdorferi spirochetes have been isolated, amblyomma americanum and Dermacentor variabilis, are abundant throughout much of Indiana. The proposed research is designed to establish: (1) whether B. burgdorferi occurs in indigenous tick populations, particularly A. americanum and D. variabilis, and, (2) whether indigenous mammal populations harbor infections of LD. In order to accomplish these objectives, ticks and mammalian blood and tissue samples will be collected from three areas of the state, and processed for study. Ticks will be identified, surface sterilized and dissected. Fixed smears of midgut diverticula will be treated with EITC-labeled conjugate and examined for spirochetes by fluorescence microscopy. Remaining tissues of positive specimens will be triturated and cultured in BSK II medium and further examined by indirect immunofluorescence using monoclonal antibody H5332. Whole blood, spleens and kidneys of small mammals trapped in each study area will be inoculated into BSK II medium and cultured. Cultures will be examined periodically for spirochetes by darkfield microscopy. Positive cultures will be further examined by indirect immunofluorescence using monoclonal antibody. All positive specimens will be stored at -70 degrees C for further characterization.